User input devices with many degrees of freedom require the user to support the mass of the input device.
One example of such a known input device is depicted in FIGS. 1-2B. FIG. 1 depicts the multi-DOF user input device 8 for the left hand of the user. To interface with the device 8, the user places the left palm on the main body 10 of the user controller 8, the forefinger on the forefinger interface 12 that is able to move relative to the main body 10 via a rotary link 14, and the thumb in the thumb groove 16. The main body 10 of the user interface 8 is connected to a multi-DOF positioning or sensing system through a linkage 18. In order to supply forces and torques to move the user interface 8 both a thumb restraint 20 and forefinger restraint 22 to constrain the users hand to the device 8.
FIGS. 2A and 2B depict the ability of the user to further input an open/close motion of the forefinger interface 12, which is connected to the main body 10 using a link 14 and rotary joint 30. The minimum displacement 32 (as shown in FIG. 2A) and maximum displacement 34 (as shown in FIG. 2B) can be measured and used as an additional control signal. The thumb restraint 20 and forefinger restraint 22 supply constraints such that the user maintains control of the main body 10 while moving the grasper throughout its range of motion. Such restraints, while enabling the user to input another control signal, make it difficult for the user to disengage with the device 8 in a controlled manner.
Further, in order for the user to exit the device in a controlled fashion, support of the input device must transferred to the input device itself or the signal being output by the device must cease. That is, during use, the input device is supported or maintained in its operable position by the hand of the user, but removal of the user's hand from the input device without any mechanical force applied by the system itself causes the input device to be pulled downward by gravity, which can result in the robotic device or component operably coupled to the input device to move or be actuated in an undesirable fashion.
There is a need in the art for improved methods and devices for detecting the presence of a user at, on, or using a user input device.